Current systems for deep well pumping involve electrical submersible pumps (“ESPs”) or geared centrifugal pumps (“GSPs”). Such pumps are the current, principal methods used as artificial lifts in high rate oil wells, where a multi-stage centrifugal pump is located downhole. For example, in an ESP system, a downhole electrical motor directly drives the pump, with electric power supplied to the motor via a cable extending from the surface to the motor's location downhole. For example, in a GSP system, the pump is driven via a rotating rod string extending from the surface to a speed increasing transmission system located downhole. The speed increasing transmission system is used to increase the relatively slow rotation of the rod string to a much faster rotation, as needed by the pump. In this example, the rod string is driven by a prime mover at the surface.
In current systems, the artificial lift system tends to be a bit burdensome. For example, in the installation of a current artificial lift system, a 300 to 400 foot artificial pump is installed in 10 foot sections in assembly form. Likewise, in the maintenance of a specific section of the pipe or tubing, the entire section of the pump must be removed all at once before any maintenance can be made.
FIGS. 1A and 1B show example line shaft pumps. FIG. 1A shows a line shaft pump with water lubricated bearings. In FIG. 1A, the drive shaft is running directly inside the production tubing, or column pipe. Unlike the example shown in FIG. 1B, this pump does not use an oil pipe. Instead, in FIG. 1A, the drive shaft is centered within the column pipe by water lubricated bearings and bearing retainers attached to the column pipe. Such bearings are typically made of rubber, due to use in water. The pump thrust, as well as the weight of the drive shaft itself, are carried by a thrust bearing located at the surface.
FIG. 1B shows a line shaft pump with an oil pipe and oil lubricated bearings. In FIG. 1B, an oil lubricated drive shaft rotates inside the oil pipe, or oil filled tubular housing. The drive shaft is supported by shaft bearings, e.g., bronze bushings, attached fixedly to the oil pipe. The bushings are spaced, e.g., 5 feet to 10 feet, on yhr oil pipe and along the drive shaft depending upon the intended rotational speed of the drive shaft. In this example, the steel pump shaft forms the journals for the bronze bushings. The pump thrust, as well as the weight of the drive shaft itself, are carried by a thrust bearing at the surface. Accordingly, the oil pipe can be centered within the column pipe by elastomer centralizers spaced evenly along its length as shown in FIG. 1B.
In both FIGS. 1A and 1B, there is a required bearing spacing for adequate support of the drive shaft. Such spacing affects the configuration of the tubulars used in installation. For example, in a water lubricated system shown in FIG. 1A, if the drive shaft bearings are required every 10 feet, then the column pipe is used in 10 foot segments. The bearing retainers are fixed to the column pipe at the column pipe couplings. For example, in an oil lubricated system shown in FIG. 1B, if the drive shaft bearings are required every 10 feet, then the oil pipe is used in 10 foot segments. The bushings are fixed to the drive shaft housing at the housing couplings. In both examples, the pump systems can be installed in similar fashion. For example, if the bearing spacing is deemed to be 10 feet, then all of the components including the column pipe, oil pipe, and drive shaft, are in 10 foot length segments. Thus, as the pump is lowered into a well, each of the 10 foot segments of the drive shaft, bearings and column or oil pipe, must be installed in 10 foot segments.
Accordingly, a need exists for a less burdensome installation, de-installation, and maintenance of a pump system for both oil and water lubrication systems.